Valve seal assembly

ABSTRACT

The present invention is directed to a valve seal assembly for use in multi-chamber vacuum devices. The seal assembly comprises a door and a deformable seal ring running along the periphery of the door, wherein the seal ring is held in place by a reversibly mounted securing means such as a disk, ring or clamp.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 10/359,374,filed Feb. 6, 2003 which is a continuation-in-part of U.S. applicationSer. No. 10/346,833, filed Jan. 17, 2003 which claims the benefit ofU.S. Provisional Application 60/353,400, filed Jan. 31 2002.

FIELD OF THE INVENTION

The present invention relates to a seal assembly for valves and inparticular to a gate valve or pendulum valve seal assembly having areplaceable deformable seal ring, said assembly finding particular usein forming a seal between chambers in vacuum equipment employed in thesemiconductor industry for chip manufacture.

BACKGROUND OF THE INVENTION

Integrated circuit (IC) chips are typically manufactured inmulti-chambered vacuum equipment. Each chamber may contain a differentenvironment, e.g. atmosphere, temperature, and pressure, than adjacentchambers. Chambers are typically isolated from each other by gate valves(or slit valves). Such valves may be utilized for moving semiconductorwafers from one chamber to another. In addition, pendulum valves may beemployed to separate chambers from a vacuum source and for the feedingor exhausting of gases. In both gate valves and pendulum valves, sealingis affected by closing a sealing member, also referred to as a disk ordoor, portion of the valve. Generally, the door comprises a metal plate,sized and shaped for covering the opening within the valve, and adeformable seal, or O-ring, mounted on the sealing surface of the door,near its periphery. The deformable seal is typically made from anelastomeric or thermoplastic polymer.

During use in the manufacture of IC chips, the deformable door seal isexposed to high temperatures and to corrosive plasmas. The latterconditions, coupled with repeated opening and closing of the door,causes the deformable seal ring to deteriorate and, eventually need tobe replaced. Deformable seal replacement has been problematic.

Early door designs featured a dovetail-shaped groove running along theperiphery of the door sealing surface. The groove was used to hold adeformable O-ring seal or a modified (O-ring (U.S. Pat. No. 5,482,297).However, in use, the deformable seal ring could undesirably pop out ofthe groove when the gate valve door was opened. It could also bedifficult and time consuming to install a replacement seal ring withinthe groove without damaging the seal.

A more recent door design is disclosed in U.S. Pat. No. 6,089,543wherein the gate valve door comprises a mounting member and a seal plateattached thereto, wherein a deformable seal ring is mounted onto theouter surface of the seal plate. In this design, the deformable sealring is preferably bonded, by molding in place, onto the seal plate.When it is desired to replace a worn deformable seal ring, the sealplate/deformable seal assembly is readily detached from the mountingmember and discarded. A new seal plate/deformable seal assembly is thenattached to the mounting member. This design has the economic andenvironmental disadvantage of not re-using the old seal plate.

U.S. Pat. No. 5,579,718 discloses a slit valve door having a removableO-ring seal that is held in place within a groove that is partiallyformed by the door and partially formed by a removable wedge insert.However, it may be difficult to install the O-ring seal in this doorgroove without twisting the O-ring. Twisting can cause premature sealfailure.

It is an object of the present invention to provide a valve door havinga securely mounted deformable seal element which may be quickly replacedwhen desired, without the need for replacing a large portion of the doorand without damaging the seal element.

SUMMARY OF THE INVENTION

The present invention is directed to a valve seal assembly for use insealing an opening in a chamber employed in vacuum equipment,particularly in semiconductor manufacturing equipment.

Specifically an aspect of the invention is a valve seal assembly for usein vacuum chambers of semiconductor manufacturing equipment, said valveassembly comprising:

a) a door having a groove for receiving a seal ring, said groove formedon a sealing surface near a periphery of said door, and wherein a firstportion of said groove is formed of a base, an outer sidewall and outerlip in said door;

b) a securing means for holding a seal ring within said groove on saiddoor, said securing means having an outer sidewall and lip which forms asecond portion of said groove;

c) fastening means for attaching said securing means to said door; and

d) a deformable seal ring shaped and sized to complementarily fit withinsaid groove, said seal ring comprising a first thin portion forcomplementarily engaging said first portion of said groove and a secondthin portion for complementarily engaging said second portion of saidgroove, and said seal ring having a thick portion located between saidfirst and second thin portions and sized to extend beyond said door lip.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a plan view of an embodiment of the seal assembly of thisinvention.

FIG. 2 is a cross-section view of an embodiment of the seal assembly ofthis invention taken along lines 2-2 of FIG. 1.

FIG. 3 is a cross-section view of another embodiment of the sealassembly of this invention taken along lines 2-2 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a plan view of the valve door seal assembly 10 of thisinvention wherein a deformable seal ring 12 is mounted in a groove nearthe periphery of the sealing surface of door 14 and held in place bysecuring means 16. By “sealing surface” is meant the surface of the doorwhich covers the opening that is sealed when the valve is closed.

FIG. 2 shows, in cross-section along 2-2, the door assembly of thisinvention. Seal ring 12 is reversibly mounted on the base 18 of a grooveon the sealing surface of door 14. The groove has an outer side wall 20and an outer lip 22 for complementarily engaging a relatively thin outerportion 30 of deformable seal ring 12. Securing means 16 has an outerside wall 24 and outer lip 26 for complementarily engaging a relativelythin inner portion 32 of deformable seal ring 12. Seal ring 12 has arelatively thick portion 34 located between thin portions 30 and 32.Thick portion 34 is generally parabolic-shaped and it is sized to extendabove the lips of both door 14 and securing means 16 for sealingengagement with the surface (i.e. mating flange) surrounding the openingin the valve (not shown). The shape of seal ring 12 results in therequirement for only a relatively minor compressive force in order toform an effective seal under high vacuum. Much more force would berequired if seal ring 12 were an O-ring.

Although securing means 16 is shown as a solid disk or wedge in thefigures, one skilled in the art would readily recognize that thesecuring means could equally be a continuous ring, a non-continuousring, or a series of brackets. Such alternate embodiments arecontemplated in this invention. Securing means 16 is reversibly attachedto door 14 by fastening means 28.

Fastening means 28 may include bolts (as shown in FIG. 2), screws, pins,adhesives, etc. Such alternative embodiments are included in the presentinvention. The number and location of fastening means required toadequately attach securing means 16 to door 14 depends upon the shapeand size of the securing means and may be readily determined by theskilled practitioner. Optionally, second seal 36 may be used withfastening means 28 (FIG. 3) to form an airtight seal between thefastening means and the door. This ensures that a vacuum leak does notoccur due to poor mating between door 14, seal ring 12 and securingmeans 16. Second seal 36 may be a washer, 0-ring, square gasket, or thelike.

Door 14 and securing means 16 can be fabricated from metals such asstainless steel, aluminum, or other non-deformable metal. The door andsecuring means may be made of the same material or of differentmaterial. Securing means 16 can also be made from polymers having eithera modulus or a hardness much greater than that of the material used asthe seal ring 12. Polymers, useful for preparation of the securing meansinclude, but are not limited to nylon, polyether ether ketone (PEEK),polyether sulfone (PES), polytetrafluoroethylene (PTFE), polyimide, oran organic or inorganic composite. Preferably the door and securingmeans are made of steel or aluminum, most preferably a stainless steelsuch as 316L, or anodized aluminum.

Seal ring 12 may be fashioned out of elastomer (preferably) or otherdeformable material such as a thermoplastic resin (e.g. copolymers oftetrafluoroethylene) that is thermally stable and inert to the plasmawhich is employed in the chip manufacturing equipment. Suitableelastomers include silicone rubber, nitrile rubber, hydrogenated nitrilerubber, EPDM, copolymers of ethylene and an alpha olefin having at leastfour carbon atoms, and fluoroelastomers, including perfluoroelastomers.For applications requiring seals that may be exposed to hightemperatures, harsh chemicals or require very low extractables, aperfluoroelastomer is the preferred elastomer. By “perfluoroelastomer”is meant copolymers comprising copolymerized units oftetrafluoroethylene and copolymerized units of a perfluoro(alkyl vinylether) or a perfluoro(alkoxy vinyl ether). Such copolymers may alsocontain a minor amount (preferably less than 7 mole percent, based onthe total number of moles of comonomers) of a cure site such as Br, I,CN, or H. Perfluoroelastomers have been extensively described in theprior art. See, for example, U.S. Pat. Nos. 4,035,565; 4,281,092;4,529,784; 4,487,903; 5,789,489; 5,936,060; 6,140,437; 6,211,319 B1 and6,281,296 B1.

Optional second seal 36 may be fashioned out of any of the materialsmentioned above as suitable for seal ring 12. However, since second seal36 is never exposed to plasmas, it need not be made from expensiveperfluoroelastomer or other plasma inert material.

Worn seal ring 12 may easily be replaced in the present invention by thesteps of a) disengaging fastening means 28, b) removing securing means16, c) replacing the worn seal ring with a new seal ring, d)repositioning securing means 16 and e) engaging fastening means 28. Thenew seal ring easily slides into the groove without twisting.

Finite Element Analysis (FEA) studies of 1) the valve seal assembly ofthe present invention in the embodiment of a slit valve and 2) the doorseal assembly of U.S. Pat. No. 5,579,718 indicate that the door seal ofthe present invention has a higher contact pressure against the matingflange (while under the same compressive load) than does the U.S. Pat.No. 5,579,718 door seal assembly. This results in better vacuum sealingperformance for the seal assembly of the present invention.

The present valve seal assembly finds use in vacuum sealingapplications, particularly in gate or slit valves and in pendulum valvesutilized in the sealing of vacuum chambers in semiconductor chipmanufacturing equipment. Besides the preferred embodiments of theinvention illustrated in the drawings and described in detail above, theskilled artisan will readily understand that the invention is capable ofalternative embodiments. For example, in order to provide space forthermal expansion of the seal ring, the groove sidewall radius, sealring width and the undercut geometry of the securing means may beadjusted. Accordingly the invention should not be strictly limited inscope to the preferred embodiments.

1. A deformable seal ring shaped and sized to complementarily fit withina groove, said groove having a first sidewall and first lip overhangingsaid first sidewall, a base, a second sidewall and second lipoverhanging said second sidewall, said seal ring comprising a first thinportion for complementarily engaging a first portion of said grooveformed by said first sidewall, base and said first lip and a second thinportion for complementarily engaging a second portion of said grooveformed by said second sidewall, base and second lip, and said seal ringhaving a thick portion located between said first and second thinportions and sized to extend beyond both said first and second sidewallsof said groove, said thick portion having a generally paraboliccross-section.
 2. A deformable seal ring of claim 1 further comprisingfirst and second portions of intermediate thickness located between saidfirst and second thin portions and said thick portion.
 3. A deformableseal ring of claim 1 wherein said first and second thin portions eachhave a generally rectangular cross-section.
 4. A deformable seal ring ofclaim 1 fashioned from an elastomer selected from the group consistingof i) silicone rubber, ii) nitrile rubber, iii) hydrogenated nitrilerubber, iv) EPDM, v) copolymers of ethylene and an alpha olefin havingat least four carbon atoms, and vi) fluoroelastomers.
 5. A deformableseal ring of claim 2 wherein said fluoroelastomer is aperfluoroelastomer.